A vacuum generating apparatus adapted to generate a negative pressure by utilizing the flow of compressed air is referred to as “ejector”. This ejector has: a nozzle for focusing the compressed air, then diffusing and ejecting the compressed air; and a diffuser coaxially aligned with the nozzle. By supplying compressed air from the nozzle to the diffuser to cause the air to flow toward an ejecting port provided in a downstream portion of the diffuser, a negative-pressure region is formed around a distal-end portion of the nozzle. If a suction port is open in this negative-pressure region, the negative pressure is generated at the suction port because of the viscosity of air.
As one example of an ejector based on this operation principle, as disclosed in Patent Document 1, an ejector attached to a pneumatic apparatus assembled with a vacuum regulator and a vacuum filter is known. The ejector of this type is adapted to supply a large amount of negative-pressure air, and has a tandem diffuser to increase the flow rate of intake air.
On the other hand, as one ejector which is used for attracting and carrying a small electronic component such as several-mm square of semiconductor chip, as disclosed in Patent Document 2, an ejector incorporated in a block is known. In the ejector of this type, a solenoid valve for vacuum generation, which controls the supply of compressed air to a nozzle of the ejector, and a solenoid valve for vacuum break, which controls the supply of compressed air for vacuum break when an electronic component is detached from an attracting tool, are assembled in the block.
In either of the ejectors of the above types, a muffler is provided so as to reduce exhaust noise caused by air discharged from an ejecting port, in other words, an exhaust port of a diffuser to the outside.